Why did you buy that?

Some new research on reasons why we buy what we buy and the benefits--conscious or otherwise--that we hope to gain from our purchases:

If marketers (or their customers) understood biologists’ new calculations about animals’ “costly signaling,” Dr. Miller says, they’d see that Harvard diplomas and iPhones send the same kind of signal as the ornate tail of a peacock.

Sometimes the message is as simple as “I’ve got resources to burn,” the classic conspicuous waste demonstrated by the energy expended to lift a peacock’s tail or the fuel guzzled by a Hummer. But brand-name products aren’t just about flaunting transient wealth. The audience for our signals — prospective mates, friends, rivals — care more about the permanent traits measured in tests of intelligence and personality, as Dr. Miller explains in his new book, “Spent: Sex, Evolution and Consumer Behavior.”